The invention relates to a process and a system of electronic injection with regulation by probe .lambda. for an internal combustion engine of the type comprising at least an injector whose opening time is controlled by a computer as a function of the operating parameters of the engine and the stage of probe .lambda..
Probe .lambda. is a sensor whose output voltage can swing between a high level (rich mixture) and a low level (poor mixture) located on both sides of a threshold corresponding to the stoichiometric ratio (richness "1"). The output signal of probe .lambda. is formatted in the injection computer and the resulting logic information is a rectangular signal to which, by convention, is assigned the value "+1" when it is at the high level and the value "-1" when it at the low level.
The regulation adapted for this type of information is the superposition of a regulation of the proportional type and a regulation of the integral type. The proportional correction makes it possible to increase the regulation frequency, while the integral correction more particularly makes it possible to go from one functioning point to another adapted differently in richness, i.e., to respond to richness mismatching.
The closed loop regulation of the injection by means of a probe .lambda. is essentially used when the exhaust system of the engine is equipped with a catalyst intended to reduce emissions of undesirable components (pollutants) of exhaust gases. Actually, this regulation makes it possible to control the richness of the air/fuel mixture admitted into the engine around the value .lambda.=1, which is an essential condition for satisfactory combustion of the toxic components by the catalyst.
The good functioning of this latter therefore requires a regulation of the mixture which is exact and exhibits the smallest possible inertia. In other words, a high regulation frequency of the probe promotes an efficient functioning of the catalyst.
For this purpose, various solutions have been proposed to optimize the terms of proportional and integral correction and, despite certain efficiencies, these solutions encounter certain limits.